CA2339810A1 - Manufacture of an optics package - Google Patents
Manufacture of an optics package Download PDFInfo
- Publication number
- CA2339810A1 CA2339810A1 CA002339810A CA2339810A CA2339810A1 CA 2339810 A1 CA2339810 A1 CA 2339810A1 CA 002339810 A CA002339810 A CA 002339810A CA 2339810 A CA2339810 A CA 2339810A CA 2339810 A1 CA2339810 A1 CA 2339810A1
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- Canada
- Prior art keywords
- optical fibre
- fibre
- fixing point
- length
- integrated optics
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 11
- 239000013307 optical fiber Substances 0.000 claims abstract description 62
- 238000000034 method Methods 0.000 claims abstract description 21
- 239000000835 fiber Substances 0.000 claims description 31
- 238000006073 displacement reaction Methods 0.000 claims description 18
- 238000005520 cutting process Methods 0.000 claims description 2
- 239000000853 adhesive Substances 0.000 claims 1
- 230000001070 adhesive effect Effects 0.000 claims 1
- 230000003287 optical effect Effects 0.000 abstract description 6
- 239000000919 ceramic Substances 0.000 description 10
- 238000005452 bending Methods 0.000 description 5
- 230000005693 optoelectronics Effects 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 239000003822 epoxy resin Substances 0.000 description 3
- 229920000647 polyepoxide Polymers 0.000 description 3
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 230000008602 contraction Effects 0.000 description 2
- 238000012938 design process Methods 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 230000001681 protective effect Effects 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 229910001369 Brass Inorganic materials 0.000 description 1
- 239000010951 brass Substances 0.000 description 1
- 238000005253 cladding Methods 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000010432 diamond Substances 0.000 description 1
- 229910003460 diamond Inorganic materials 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000010437 gem Substances 0.000 description 1
- 229910001751 gemstone Inorganic materials 0.000 description 1
- 239000012212 insulator Substances 0.000 description 1
- 229910000833 kovar Inorganic materials 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 239000011253 protective coating Substances 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/015—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on semiconductor elements having potential barriers, e.g. having a PN or PIN junction
- G02F1/025—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on semiconductor elements having potential barriers, e.g. having a PN or PIN junction in an optical waveguide structure
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/30—Optical coupling means for use between fibre and thin-film device
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/36—Mechanical coupling means
- G02B6/38—Mechanical coupling means having fibre to fibre mating means
- G02B6/3807—Dismountable connectors, i.e. comprising plugs
- G02B6/381—Dismountable connectors, i.e. comprising plugs of the ferrule type, e.g. fibre ends embedded in ferrules, connecting a pair of fibres
- G02B6/3818—Dismountable connectors, i.e. comprising plugs of the ferrule type, e.g. fibre ends embedded in ferrules, connecting a pair of fibres of a low-reflection-loss type
- G02B6/3821—Dismountable connectors, i.e. comprising plugs of the ferrule type, e.g. fibre ends embedded in ferrules, connecting a pair of fibres of a low-reflection-loss type with axial spring biasing or loading means
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Nonlinear Science (AREA)
- Optical Couplings Of Light Guides (AREA)
- Mechanical Coupling Of Light Guides (AREA)
- Light Guides In General And Applications Therefor (AREA)
Abstract
A method of making an optics package is described in which an exposed length of optical fibre (10) is deliberately subject to a predetermined bend. The relationship between the exposed length of the optical fibre and a distance between a location at which it is supported (P2) and a fixing point (P1) on an optical device (4) is determined taking into account the induced strain in t he optical fibre. An optics package designed according to the method is also se t forward.
Description
MANUFACTURE OF AN OPTICS PACKAGE
The present invention relates to a method of making an optics package in particular of. the type in which a length of optical fibre is fixed to an integrated optics device.
The present invention is particularly but not exclusively concerned with the packaging of integrated opto-electronic devices which comprise a silicon-on-insulator wafer in which are monolithically formed optical waveguides. These waveguides are defined in the surface of the silicon itself . The integrated optics device can also include electronic or optoelectronic components which axe secured to the surface of the wafer. The optical fibre acts as a conduit for light onto and off the integrated optics device. It is supported within the package by an entry ferrule and extends from that to a fixing point on the integrated optics device. The design of reliable optoelectronics devices requires that the end fixtures of the optical fibre do not experience excessive forces during package temperature changes nor that the optical fibre experiences excessive strain levels.
The present invention seeks to provide a method of manufacture which attains these objectives.
According to the present invention there is provided a method of making an optics package in which an exposed length of optical fibre extends between a supported location and a fixing point on an integrated optics device wherein the relationship between the exposed length (L) of the optical fibre and a distance (~h) between the supported location and the fixing point on a mutually perpendicular axis is determined taking into account the induced strain in the optical fibre so that, on assembly, a predetermined bend is introduced into the exposed length of optical fibre.
The package includes a casing which has a part holding an integrated optics device and an entry part within which the optical fibre is supported at the supported location. In a situation where the casing is manufactured first, the method comprises the step of determining the vertical offset (~h) inherent in the casing between the fixing point on the integrated optics device and the supported location. The required exposed length (L) of optical fibre is then calculated taking into account the induced strain limitations.
According to the described embodiment, the method also comprises assembling a fibre optics structure by inserting a length of optical fibre through a supporting element, cutting the length of optical fibre to the required exposed length (L), receiving the fibre optics structure in the casing which holds the integrated optics device, and fixing the optical fibre to the fixing point. The supporting element is termed herein a ferrule and comprises in the preferred embodiment a metallic outer casing housing a ceramic insert through which the optical fibre extends, as described for example in our earlier British Application No.
9814643.4.
It has been found that it is possible to design a package wherein the maximum induced strain E",ax is kept to 0.3% or below, where:
X = r x 100, R
R being the minimum bending radius, even when small longitudinal displacements are incurred in use due to thermal expansion and/or assembly errors.
One way of achieving this is to utilise a design technique which relies on an empirically determined design strain Eden as discussed in more detail in relation to the preferred embodiment .
Another way of achieving this for packages of the approximate dimensions discussed herein is to rely on the following equation:
The present invention relates to a method of making an optics package in particular of. the type in which a length of optical fibre is fixed to an integrated optics device.
The present invention is particularly but not exclusively concerned with the packaging of integrated opto-electronic devices which comprise a silicon-on-insulator wafer in which are monolithically formed optical waveguides. These waveguides are defined in the surface of the silicon itself . The integrated optics device can also include electronic or optoelectronic components which axe secured to the surface of the wafer. The optical fibre acts as a conduit for light onto and off the integrated optics device. It is supported within the package by an entry ferrule and extends from that to a fixing point on the integrated optics device. The design of reliable optoelectronics devices requires that the end fixtures of the optical fibre do not experience excessive forces during package temperature changes nor that the optical fibre experiences excessive strain levels.
The present invention seeks to provide a method of manufacture which attains these objectives.
According to the present invention there is provided a method of making an optics package in which an exposed length of optical fibre extends between a supported location and a fixing point on an integrated optics device wherein the relationship between the exposed length (L) of the optical fibre and a distance (~h) between the supported location and the fixing point on a mutually perpendicular axis is determined taking into account the induced strain in the optical fibre so that, on assembly, a predetermined bend is introduced into the exposed length of optical fibre.
The package includes a casing which has a part holding an integrated optics device and an entry part within which the optical fibre is supported at the supported location. In a situation where the casing is manufactured first, the method comprises the step of determining the vertical offset (~h) inherent in the casing between the fixing point on the integrated optics device and the supported location. The required exposed length (L) of optical fibre is then calculated taking into account the induced strain limitations.
According to the described embodiment, the method also comprises assembling a fibre optics structure by inserting a length of optical fibre through a supporting element, cutting the length of optical fibre to the required exposed length (L), receiving the fibre optics structure in the casing which holds the integrated optics device, and fixing the optical fibre to the fixing point. The supporting element is termed herein a ferrule and comprises in the preferred embodiment a metallic outer casing housing a ceramic insert through which the optical fibre extends, as described for example in our earlier British Application No.
9814643.4.
It has been found that it is possible to design a package wherein the maximum induced strain E",ax is kept to 0.3% or below, where:
X = r x 100, R
R being the minimum bending radius, even when small longitudinal displacements are incurred in use due to thermal expansion and/or assembly errors.
One way of achieving this is to utilise a design technique which relies on an empirically determined design strain Eden as discussed in more detail in relation to the preferred embodiment .
Another way of achieving this for packages of the approximate dimensions discussed herein is to rely on the following equation:
.L lies in the range 100 x /3r to 100 x ~3r ~h J io where r is the fibre radius. This has been found in practice to be a robust guide fox the relationship between the exposed length L and the distance 0h in an optoelectronic package.
The optical fibre can be fixed to the integrated optics device by inserting the f fibre optics structure into the casing, with the free end of the optical fibre located just above the integrated optics device held in the casing, and then pushing the free end of the optical fibre downwards into a groove at the fixing point on the integrated optics device. The optical fibre can be secured by epoxy resin at the fixing point. This provides a so-called positive S-bend which eases assembly and produces a downwards force at the tip of the fibre in front of the fixing point.
The integrated optics device can be located within the casing on a base component such as a ceramic wafer.
According to the specific embodiment described herein, a design method is disclosed in which the optical fibre is intentionally assembled with a vertical offset Oh between the end fixing points thereby forcing the fibre to take up a gentle positive S bend shape of known geometry. The important aspect.of the S bend is that, despite the small additional strain induced in the fibre due to the bending moment from the vertical offset, compressive or tensile forces experienced by the end fixing points remain substantially constant and at a known level. This is important as the end fixings, particularly to the integrated optics device, can be relatively weak because of the limited surface area that is available to form bond surfaces. Moreover, the expected strain can be predetermined to be below a level at which short term failure would occur, that is preferably no greater than 0.3%
The optical fibre can be fixed to the integrated optics device by inserting the f fibre optics structure into the casing, with the free end of the optical fibre located just above the integrated optics device held in the casing, and then pushing the free end of the optical fibre downwards into a groove at the fixing point on the integrated optics device. The optical fibre can be secured by epoxy resin at the fixing point. This provides a so-called positive S-bend which eases assembly and produces a downwards force at the tip of the fibre in front of the fixing point.
The integrated optics device can be located within the casing on a base component such as a ceramic wafer.
According to the specific embodiment described herein, a design method is disclosed in which the optical fibre is intentionally assembled with a vertical offset Oh between the end fixing points thereby forcing the fibre to take up a gentle positive S bend shape of known geometry. The important aspect.of the S bend is that, despite the small additional strain induced in the fibre due to the bending moment from the vertical offset, compressive or tensile forces experienced by the end fixing points remain substantially constant and at a known level. This is important as the end fixings, particularly to the integrated optics device, can be relatively weak because of the limited surface area that is available to form bond surfaces. Moreover, the expected strain can be predetermined to be below a level at which short term failure would occur, that is preferably no greater than 0.3%
For a better understanding of the present invention and to show how the same may be carried into effect, reference will now be made by way of example to the accompanying drawings in which:
Figure 1 is a partial section through an optics package;
Figure 2 is a diagram illustrating an S-bend;
Figure 3 is an enlarged portion of the fixing point for the optical fibre in the integrated optics device;
Figure 4 illustrates the parameters of the S-bend for the design process; and Figure 5 is a graph of strain vs displacement for different S-bend configurations.
Figure 1 illustrates an optics package which comprises a casing 2 for example formed of KOVAR (Ni/Fe/Co) or another material with a high hermeticity. The casing 2 has a bowl-shaped part 2a for receiving an integrated optics device 4 on a ceramic wafer 6.
The casing 2 also has a tubular entry part 2b. Although not shown, in its final form the package includes a lid so that the entire package is hermetically sealed. The entry part 2b holds a ferrule 8 which comprises a metallic outer casing, for example of brass, which holds a ceramic insert having a central bore through which extends an optical fibre 10. The optical fibre forms part of a fibre optic cable 12. The fibre optic cable 12 has a central optics core surrounded by optical cladding, and a number of protective outer layers. The optical fibre 10 has been stripped of the protective outer layers. The ferrule 8 provides a hermetically sealed structure into which the fibre optic cable 12 is inserted at one end and the optical fibre 10 protrudes from the other end. The bold line marked 10 in Figure 1 illustrates the optical fibre in the form which it takes up in the finished package. As can be seen, this is in the form of a gentle S bend.
The dotted line in Figure 1 illustrates the optical fibre 10 during assembly as will be described in more detail hereinafter.
The integrated optical device 4 has formed on its surface monolithically a number of silicon waveguides. In addition, it has a micro-machined V groove 14 in which the end portion of the S
fibre 10 is located adjacent its fixing point.
Figure 2 represents the important components of the S bend in more detail. The distance oh represents a vertical offset between the fixing point P1 of the optical fibre to the integrated optics device and a supported location P2 which is the point at which the optical fibre 10 exits the ferrule 8. The vertical offset ~h is introduced by virtue of the fact that the central axis of the ferrule .8 is displaced vertically from the upper surface of the integrated optics device 4 so that, during assembly, the end of the optical fibre 10 remote from the ferrule 8 has to be pushed downwards onto the integrated optics device 4. Thus it can be seen that the vertical offset Oh is principally defined by the parameters of the casing 2.
The other important dimension is the "exposed" length L of optical fibre 10, this being the length between the fixing point P1 and the supported location P2. As defined herein, the length L is the horizontal distance between P1 and P2. As a matter of practicality, the actual length L' of the optical fibre is very close to the horizontal length L because the offset ~h is very small in comparison to the length L.
Figure 3 illustrates the fixing location at the integrated optical device in more detail. The optical fibre 10 is pressed into the V groove 14 and secured there by epoxy resin 16. In Figure 3, the optical fibre 10 is illustrated as passing through a ceramic disc 18, for example a watchmaker's jewel (as described in our earlier GB Patent 2313676B, which is also secured to the side of the integrated optics device. This provides resistance against peeling forces of the optical fibre.
A method of manufacturing the package illustrated in Figure 1 will now be described.
A casing 2 is provided having the form illustrated in Figure 1, in particular with the bowl-shaped receiving part 2a and entry part 2b. There is sufficient depth of the receiving part 2a to allow for receiving a ceramic wafer 6 supporting an integrated optics circuit 4 and to allow an extra distance oh up to the horizontal central axis of the entry part 2b. The ceramic wafer 6 and integrated optics device 4 are located and secured within the casing 2.
A fibre optics structure is prepared by stripping the outer protective coatings from a fibre optic cable to provide a stripped length 10 of optical fibre. This is inserted through a ceramic insert held within a metallic tube constituting the ferrule 8. The required length L' of the optical fibre 10 in the finished package is calculated as described further herein. The actual length of optical fibre 10 extending from the ferrule 8 after assembly is cut down to the required exposed length L'.
The ceramic disc 18 is threaded onto the free end of the optical fibre. The ferrule 8 is then inserted within the entry part 2b of the casing so that the optical fibre 10 extends along the axis of the entry part 2b and protrudes into the receiving part 2a.
At this point, the optical fibre 10 has the profile shown as a dotted line in Figure 1, that is with its free end located above the fixing point of the integrated optical circuit. The optical fibre is then pushed downwards into the V groove 14 and secured there by bonding with epoxy resin. In this manner, a positive S bend is deliberately introduced into the optical fibre.
The stress and strain parameters of the optical fibre are determined by the configuration of the S bend and its expected displacement during use. The most significant factor affecting longitudinal displacement are the thermal expansion coefficients of the metal used for the casing 2 and the metal used for the ferrule 8 and therefore these need to be taken into account during the design process . In fact, it has been demonstrated that if adequate account is taken of the strain parameter, small displacements are also dealt with.
A process for calculating the maximum tensile fibre strain will now be described with reference to Figure 4. In Figure 4, the solid line represents the horizontal distance L between the fixing points P1 and P2, and this approximates to the length L' of the optical fibre 10.. oh represents the vertical offset as already described. ~z represents the axial distance of the fibre which may occur due to fixing errors in assembly and the effects of thermal expansion and contraction. An extension of the length L to put the fibre into tension is denoted herein as a positive value for ~z, and a decrease to put the fibre into compression is noted as a negative value. 8 represents an angular displacement of the ferrule at fixing point P2. That is, although during manufacture it is desirable to locate the ferrule with zero angular displacement, that is directly along the longitudinal axis of the entry part 2b of the package, errors in manufacture sometimes mean that there is a small angular displacement of the ferrule away from the axis. This is represented by the angle a in Figure 4. The axial displacement ~z represents not only the likely displacement due to thermal contraction or expansion in use, but also possible errors in location of the fixing point P2 during manufacture. As a matter of practicality, the configuration of the S bend can be designed without explicitly taking into account ~z or 8. It is possible to assemble a package so that parallel fixing points can generally be achieved, which means that a is zero or close to zero in the majority of practical cases. Also, it has been established that if the strain parameters are properly dealt with as discussed in the following sufficient tolerance is provided for 0z under normal circumstances. A correct analysis of the configuration of the S bend based on the strain parameters also deals with the likely effect of horizontal displacements. This is discussed in more detail later herein.
The design technique will now be outlined. It is important that the S bend in the final package is a so-called positive S bend, that is as illustrated in Figure 2. In order to accomplish this, a vertical offset 0h is first selected which is sufficiently large to ensure that the configuration of the fibre will be a g positive S bend. The thickness of the ceramic wafer 6 and semiconductor wafer implementing the optics device 4 are then taken into account so that a suitable casing can be selected which implements the vertical offset oh.
The length L' of the optical fibre can then be calculated according to the following equation:
J3 rE~h I' - Qdes where r is the fibre radius, E is Youngs modulus and Qaes is the design target stress in the fibre in the absence of a horizontal displacement Oz or angular displacement e.
A detailed discussion of the analysis of stresses and strains in a fibre optic interconnect subject to bending which forms the basis of this equation can be found in an article entitled "Predicted curvatures and stresses in a fibre optic interconnect subject to bending", by E. suhir, Journal of Lightwave Technology, vol. 40, no. 2, February 1996.
The design stress Qdes is calculated according to the following equation:
Qdes - E X E des where E is Youngs modulus for the f fibre and Eden is an empirically determined value for the strain such that the maximum strain under normal circumstances including small horizontal and angular displacements is no greater then 0.3%. The inventors have determined that for packages of the size described herein, Edes lies between 0.01% and 0.1% and preferably between 0.02% and 0.05%.
In order to have adequate reliability and lifetimes for an optical fibre, the maximum strain EmaX should not be allowed to exceed .3%.
A general purpose modelling program from ALGOR, Inc. was used to run a finite element model modelling the S-bend in order to determine its stress and strain characteristics based on the above-defined design technique.
A change in ~z to .02 microns to .04 microns was modelled in steps of .005 microns over a period of one second. The model output corresponding values for the axial force T in the fibre due to each displacement value 0z and the maximum bending moment M",aX. From these values, the total maximum tensile strain in the fibre as a percentage was worked out.
The results are shown in the graph of Figure 5. Figure 5 is a plot of the displacement ~z from .04 microns to .02 microns against the maximum tensile strain in the fibre. The graph has a total of six plots. The diamond, square and triangular plots denote a length L of 10 mm, at angular errors 0 of 0°, 0.5° and 1° respectively. The plots x, * and o are for lengths L of 15.5 mm, again at respective angular errors A of 0°, .5° and 1°.
The other parameters for the plot of Figure 5 are:
radius r = .0625 mm Youngs modulus E = 73,000 offset Oh = .25 mm Thus, it can be seen that by selecting a suitable design strain in the above range a wide range of horizontal displacements ~z can be accommodated without affecting the lifetime of the product because the maximum strain in the fibre does not exceed 0.3%.
Figure 1 is a partial section through an optics package;
Figure 2 is a diagram illustrating an S-bend;
Figure 3 is an enlarged portion of the fixing point for the optical fibre in the integrated optics device;
Figure 4 illustrates the parameters of the S-bend for the design process; and Figure 5 is a graph of strain vs displacement for different S-bend configurations.
Figure 1 illustrates an optics package which comprises a casing 2 for example formed of KOVAR (Ni/Fe/Co) or another material with a high hermeticity. The casing 2 has a bowl-shaped part 2a for receiving an integrated optics device 4 on a ceramic wafer 6.
The casing 2 also has a tubular entry part 2b. Although not shown, in its final form the package includes a lid so that the entire package is hermetically sealed. The entry part 2b holds a ferrule 8 which comprises a metallic outer casing, for example of brass, which holds a ceramic insert having a central bore through which extends an optical fibre 10. The optical fibre forms part of a fibre optic cable 12. The fibre optic cable 12 has a central optics core surrounded by optical cladding, and a number of protective outer layers. The optical fibre 10 has been stripped of the protective outer layers. The ferrule 8 provides a hermetically sealed structure into which the fibre optic cable 12 is inserted at one end and the optical fibre 10 protrudes from the other end. The bold line marked 10 in Figure 1 illustrates the optical fibre in the form which it takes up in the finished package. As can be seen, this is in the form of a gentle S bend.
The dotted line in Figure 1 illustrates the optical fibre 10 during assembly as will be described in more detail hereinafter.
The integrated optical device 4 has formed on its surface monolithically a number of silicon waveguides. In addition, it has a micro-machined V groove 14 in which the end portion of the S
fibre 10 is located adjacent its fixing point.
Figure 2 represents the important components of the S bend in more detail. The distance oh represents a vertical offset between the fixing point P1 of the optical fibre to the integrated optics device and a supported location P2 which is the point at which the optical fibre 10 exits the ferrule 8. The vertical offset ~h is introduced by virtue of the fact that the central axis of the ferrule .8 is displaced vertically from the upper surface of the integrated optics device 4 so that, during assembly, the end of the optical fibre 10 remote from the ferrule 8 has to be pushed downwards onto the integrated optics device 4. Thus it can be seen that the vertical offset Oh is principally defined by the parameters of the casing 2.
The other important dimension is the "exposed" length L of optical fibre 10, this being the length between the fixing point P1 and the supported location P2. As defined herein, the length L is the horizontal distance between P1 and P2. As a matter of practicality, the actual length L' of the optical fibre is very close to the horizontal length L because the offset ~h is very small in comparison to the length L.
Figure 3 illustrates the fixing location at the integrated optical device in more detail. The optical fibre 10 is pressed into the V groove 14 and secured there by epoxy resin 16. In Figure 3, the optical fibre 10 is illustrated as passing through a ceramic disc 18, for example a watchmaker's jewel (as described in our earlier GB Patent 2313676B, which is also secured to the side of the integrated optics device. This provides resistance against peeling forces of the optical fibre.
A method of manufacturing the package illustrated in Figure 1 will now be described.
A casing 2 is provided having the form illustrated in Figure 1, in particular with the bowl-shaped receiving part 2a and entry part 2b. There is sufficient depth of the receiving part 2a to allow for receiving a ceramic wafer 6 supporting an integrated optics circuit 4 and to allow an extra distance oh up to the horizontal central axis of the entry part 2b. The ceramic wafer 6 and integrated optics device 4 are located and secured within the casing 2.
A fibre optics structure is prepared by stripping the outer protective coatings from a fibre optic cable to provide a stripped length 10 of optical fibre. This is inserted through a ceramic insert held within a metallic tube constituting the ferrule 8. The required length L' of the optical fibre 10 in the finished package is calculated as described further herein. The actual length of optical fibre 10 extending from the ferrule 8 after assembly is cut down to the required exposed length L'.
The ceramic disc 18 is threaded onto the free end of the optical fibre. The ferrule 8 is then inserted within the entry part 2b of the casing so that the optical fibre 10 extends along the axis of the entry part 2b and protrudes into the receiving part 2a.
At this point, the optical fibre 10 has the profile shown as a dotted line in Figure 1, that is with its free end located above the fixing point of the integrated optical circuit. The optical fibre is then pushed downwards into the V groove 14 and secured there by bonding with epoxy resin. In this manner, a positive S bend is deliberately introduced into the optical fibre.
The stress and strain parameters of the optical fibre are determined by the configuration of the S bend and its expected displacement during use. The most significant factor affecting longitudinal displacement are the thermal expansion coefficients of the metal used for the casing 2 and the metal used for the ferrule 8 and therefore these need to be taken into account during the design process . In fact, it has been demonstrated that if adequate account is taken of the strain parameter, small displacements are also dealt with.
A process for calculating the maximum tensile fibre strain will now be described with reference to Figure 4. In Figure 4, the solid line represents the horizontal distance L between the fixing points P1 and P2, and this approximates to the length L' of the optical fibre 10.. oh represents the vertical offset as already described. ~z represents the axial distance of the fibre which may occur due to fixing errors in assembly and the effects of thermal expansion and contraction. An extension of the length L to put the fibre into tension is denoted herein as a positive value for ~z, and a decrease to put the fibre into compression is noted as a negative value. 8 represents an angular displacement of the ferrule at fixing point P2. That is, although during manufacture it is desirable to locate the ferrule with zero angular displacement, that is directly along the longitudinal axis of the entry part 2b of the package, errors in manufacture sometimes mean that there is a small angular displacement of the ferrule away from the axis. This is represented by the angle a in Figure 4. The axial displacement ~z represents not only the likely displacement due to thermal contraction or expansion in use, but also possible errors in location of the fixing point P2 during manufacture. As a matter of practicality, the configuration of the S bend can be designed without explicitly taking into account ~z or 8. It is possible to assemble a package so that parallel fixing points can generally be achieved, which means that a is zero or close to zero in the majority of practical cases. Also, it has been established that if the strain parameters are properly dealt with as discussed in the following sufficient tolerance is provided for 0z under normal circumstances. A correct analysis of the configuration of the S bend based on the strain parameters also deals with the likely effect of horizontal displacements. This is discussed in more detail later herein.
The design technique will now be outlined. It is important that the S bend in the final package is a so-called positive S bend, that is as illustrated in Figure 2. In order to accomplish this, a vertical offset 0h is first selected which is sufficiently large to ensure that the configuration of the fibre will be a g positive S bend. The thickness of the ceramic wafer 6 and semiconductor wafer implementing the optics device 4 are then taken into account so that a suitable casing can be selected which implements the vertical offset oh.
The length L' of the optical fibre can then be calculated according to the following equation:
J3 rE~h I' - Qdes where r is the fibre radius, E is Youngs modulus and Qaes is the design target stress in the fibre in the absence of a horizontal displacement Oz or angular displacement e.
A detailed discussion of the analysis of stresses and strains in a fibre optic interconnect subject to bending which forms the basis of this equation can be found in an article entitled "Predicted curvatures and stresses in a fibre optic interconnect subject to bending", by E. suhir, Journal of Lightwave Technology, vol. 40, no. 2, February 1996.
The design stress Qdes is calculated according to the following equation:
Qdes - E X E des where E is Youngs modulus for the f fibre and Eden is an empirically determined value for the strain such that the maximum strain under normal circumstances including small horizontal and angular displacements is no greater then 0.3%. The inventors have determined that for packages of the size described herein, Edes lies between 0.01% and 0.1% and preferably between 0.02% and 0.05%.
In order to have adequate reliability and lifetimes for an optical fibre, the maximum strain EmaX should not be allowed to exceed .3%.
A general purpose modelling program from ALGOR, Inc. was used to run a finite element model modelling the S-bend in order to determine its stress and strain characteristics based on the above-defined design technique.
A change in ~z to .02 microns to .04 microns was modelled in steps of .005 microns over a period of one second. The model output corresponding values for the axial force T in the fibre due to each displacement value 0z and the maximum bending moment M",aX. From these values, the total maximum tensile strain in the fibre as a percentage was worked out.
The results are shown in the graph of Figure 5. Figure 5 is a plot of the displacement ~z from .04 microns to .02 microns against the maximum tensile strain in the fibre. The graph has a total of six plots. The diamond, square and triangular plots denote a length L of 10 mm, at angular errors 0 of 0°, 0.5° and 1° respectively. The plots x, * and o are for lengths L of 15.5 mm, again at respective angular errors A of 0°, .5° and 1°.
The other parameters for the plot of Figure 5 are:
radius r = .0625 mm Youngs modulus E = 73,000 offset Oh = .25 mm Thus, it can be seen that by selecting a suitable design strain in the above range a wide range of horizontal displacements ~z can be accommodated without affecting the lifetime of the product because the maximum strain in the fibre does not exceed 0.3%.
Claims (13)
1. A method of making an optics package in which an exposed length of optical fibre extends in the direction of a first axis between a supported location and a fixing point on as integrated optics device, the supported location being additionally offset from the fixing point in the direction of a second axis perpendicular to the first, wherein the relationship between the exposed length (L') of the optical fibre and a distance (.DELTA.h) between the supported location and the fixing point on a the second axis is determined taking into account the induced strain in the optical fibre so that, on assembly, a predetermined bend is introduced into the exposed length of optical fibre.
2. A method according to claim 1, which comprises the step of determining the distance (.DELTA.h) in a casing designed to hold the integrated optics device and optical fibre and then calculating the required exposed length (L') of optical fibre.
3. A method according to claim 1,which comprises assembling a fibre optic structure by inserting a length of optical fibre through a supporting element, cutting the length of optical fibre to the required exposed length (L'), receiving the fibre optic structure in a casing which holds the integrated optics device, and fixing the optical fibre to the fixing point.
4. A method according to claim 2 or 3, wherein the exposed length is calculated according to the following:
where r is the fibre radius, E is Youngs modulus .sigma.des is a deign target stress in the absence of an angular or horizontal displacement with respect to the length direction.
where r is the fibre radius, E is Youngs modulus .sigma.des is a deign target stress in the absence of an angular or horizontal displacement with respect to the length direction.
5. A method according to claim 4, wherein the design target stress .sigma.des is calculated according to the following:
.sigma.des = E x .epsilon.des, where .epsilon.des lies in the range .01% to .1%.
.sigma.des = E x .epsilon.des, where .epsilon.des lies in the range .01% to .1%.
6. A method according to claim 5, where .epsilon.des is in the range .02% to .05%.
7. A method according to any of claims 1 to 3, wherein the relationship between the exposed length (L') of the optical fibre and the distance (.DELTA.h) is calculated according to the following:
lies in the range 100 x to 100 x where r is the fibre radius.
lies in the range 100 x to 100 x where r is the fibre radius.
8. A method according to any of claims 3 to 7, wherein the optical fibre is fixed to the fixing point by bonding with adhesive. ~I
9. A method according to any of claims 3 to 8, wherein the optical fibre is passed through a disc prior to fixing at the fixing point, the disc being secured to the integrated optics device.
10. A method according to any of claims 3 to 9, wherein the optical fibre is gushed downwards into a groove at the fixing point on the integrated optics device.
11. A method according to any of claims 2 to 10, wherein the integrated optics deice is located in the casing by securement to a base component.
12. A method according to any preceding claim, wherein the induced strain is designed to be below 0.3%.
13. A method substantially as herein described with reference to the accompanying drawings.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9817562.3 | 1998-08-12 | ||
| GB9817562A GB2340620B (en) | 1998-08-12 | 1998-08-12 | Manufacture of an optics package |
| PCT/GB1999/001494 WO2000010045A1 (en) | 1998-08-12 | 1999-05-12 | Manufacture of an optics package |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2339810A1 true CA2339810A1 (en) | 2000-02-24 |
Family
ID=10837130
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002339810A Abandoned CA2339810A1 (en) | 1998-08-12 | 1999-05-12 | Manufacture of an optics package |
Country Status (10)
| Country | Link |
|---|---|
| US (1) | US6312165B1 (en) |
| EP (1) | EP1105762A1 (en) |
| JP (1) | JP2002522815A (en) |
| KR (1) | KR20010072360A (en) |
| CN (1) | CN1312917A (en) |
| AU (1) | AU3839499A (en) |
| CA (1) | CA2339810A1 (en) |
| GB (1) | GB2340620B (en) |
| IL (1) | IL141178A0 (en) |
| WO (1) | WO2000010045A1 (en) |
Families Citing this family (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1998045741A1 (en) * | 1997-04-08 | 1998-10-15 | Hitachi, Ltd. | Optical module, method for manufacturing optical module, and optical transmission device |
| JP4167378B2 (en) * | 2000-03-28 | 2008-10-15 | 京セラ株式会社 | Optical element module |
| US6614965B2 (en) | 2001-05-11 | 2003-09-02 | Lightcross, Inc. | Efficient coupling of optical fiber to optical component |
| GB2376307B (en) * | 2001-06-07 | 2003-05-14 | Melles Griot Ltd | Fibre rotation devices and methods |
| GB2381084A (en) * | 2001-12-19 | 2003-04-23 | Bookham Technology Plc | Bent optical fibre located on substrate and connecting to optical device |
| GB2387446A (en) * | 2002-04-08 | 2003-10-15 | Bookham Technology Plc | Retainer for an optical fibre to an optical chip |
| GB2388204A (en) * | 2002-05-02 | 2003-11-05 | Bookham Technology Plc | Connecting optic fibre in elastic deformation to optical device |
| US20090257719A1 (en) * | 2008-04-09 | 2009-10-15 | Lockheed Martin Corporation | Low loss self centering fiber optic connector |
| JP2011107444A (en) * | 2009-11-18 | 2011-06-02 | Anritsu Corp | Optical element module and method for manufacturing the same |
| JP5300752B2 (en) * | 2010-01-20 | 2013-09-25 | 日本電信電話株式会社 | Light modulator |
| CN103443681A (en) | 2011-04-13 | 2013-12-11 | 株式会社藤仓 | Manufacturing method for optical module |
| JP5708465B2 (en) * | 2011-12-12 | 2015-04-30 | 日立金属株式会社 | Optical fiber connection component and optical fiber connection module |
| US11209598B2 (en) * | 2019-02-28 | 2021-12-28 | International Business Machines Corporation | Photonics package with face-to-face bonding |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4803361A (en) * | 1986-05-26 | 1989-02-07 | Hitachi, Ltd. | Photoelectric device with optical fiber and laser emitting chip |
| US5018817A (en) * | 1987-07-24 | 1991-05-28 | Brother Kogyo Kabushiki Kaisha | Method of optically coupling optical fiber to waveguide on substrate, and optical device produced by the method |
| US5268986A (en) * | 1991-09-09 | 1993-12-07 | Sumitomo Electric Industries, Ltd. | Redundant length treatment mechanism for optical fiber at terminal of optical cable |
| US5694506A (en) | 1995-03-09 | 1997-12-02 | Nippon Telegraph And Telephone Corporation | Optical connector |
| JP2910696B2 (en) * | 1996-09-20 | 1999-06-23 | 日本電気株式会社 | Semiconductor photodetector |
| GB2313676B (en) * | 1997-03-07 | 1998-04-08 | Bookham Technology Ltd | Attachment of an optical fibre |
| JPH11202155A (en) | 1998-01-12 | 1999-07-30 | Sumitomo Electric Ind Ltd | Optical fiber connector |
-
1998
- 1998-08-12 GB GB9817562A patent/GB2340620B/en not_active Expired - Fee Related
- 1998-10-20 US US09/175,848 patent/US6312165B1/en not_active Expired - Fee Related
-
1999
- 1999-05-12 AU AU38394/99A patent/AU3839499A/en not_active Abandoned
- 1999-05-12 IL IL14117899A patent/IL141178A0/en unknown
- 1999-05-12 KR KR1020017001707A patent/KR20010072360A/en not_active Application Discontinuation
- 1999-05-12 EP EP99921020A patent/EP1105762A1/en not_active Withdrawn
- 1999-05-12 CA CA002339810A patent/CA2339810A1/en not_active Abandoned
- 1999-05-12 CN CN99809536A patent/CN1312917A/en active Pending
- 1999-05-12 JP JP2000565429A patent/JP2002522815A/en active Pending
- 1999-05-12 WO PCT/GB1999/001494 patent/WO2000010045A1/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| US6312165B1 (en) | 2001-11-06 |
| AU3839499A (en) | 2000-03-06 |
| KR20010072360A (en) | 2001-07-31 |
| GB2340620B (en) | 2002-12-31 |
| GB9817562D0 (en) | 1998-10-07 |
| WO2000010045A1 (en) | 2000-02-24 |
| EP1105762A1 (en) | 2001-06-13 |
| CN1312917A (en) | 2001-09-12 |
| JP2002522815A (en) | 2002-07-23 |
| IL141178A0 (en) | 2002-02-10 |
| GB2340620A (en) | 2000-02-23 |
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Legal Events
| Date | Code | Title | Description |
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| FZDE | Discontinued |